How to replace thermocouple:

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How to replace thermocouple (or thermopile), when burner must be removed

	Caution: If you smell gas Do NOT remove combustion door and expose gas to flame inside water heater Leave house immediately. Do not touch light switch on-or-off. Do not touch anything to cause static spark. Do not pick up phone. Call gas company from outside house. NG natural gas is lighter than air and will rise to nose level, or can gather on ceiling Propane LP gas is heavier than air and will hug floor. Do not install LP propane heater below grade (in basement) or gas leak can fill basement will explosive gas. Water heater safety precautions
	Before spending money, check if pilot is ON Pilot light is hard to see through sight glass. Pilot flame is upward from sight glass. Look into sight glass, and look upward. Or use mirror to help look through sight glass so you do not have to sit on floor. Flame should be clear blue. Yellow flame indicates thermocouple is fine, but burner parts are dirty, vent is obstructed, or inadequate air supply, or dirty air intake
	Before spending money, push in TCO Newer models may have TCO located on front of combustion chamber Temperature cut off will trip if temperatures inside combustion chamber exceed limit. Wires on TCO are connected to gas control valve and prevent water heater from igniting. Causes of tripped TCO include poor venting, dirty combustion parts, inadequate air supply to the water heater, clogged air intake Buy: Thermal reset Resource: Test ECO
	Flammable vapor sensor SP20172 FV sensor reacts to gasoline vapors, shuts off gas control valve, and water heater will not work. Pilot will not light .. replace sensor FV sensor is not same as FVIR. FVIR is located inside water heater combustion chamber and responds to to all types of flammable vapors including gasoline Buy: FV sensor at Amazon Flammable sensor kit Resources: How flammable vapor sensor works Flammable vapor .pdf Who makes the most easily resettable FVIR
Buy: Flame trap inspection mirror at Amazon	Before spending money, get some air Do NOT underestimate need for adequate air and clean air intake. Save many $ up front right now. 1) Get more fresh air to water heater, especially in very hot location such as attic 2) Clean air intake so combustion can take place Illustration on left applies to AO Smith, American, State, Reliance, Craftmaster, Kenmore, Whirlpool. Other brands, and other models, might require removal of combustion parts to access arrestor screen. Test thermocouple How to test thermocouple Test thermocouple and thermopile service manual/ pdf How to troubleshoot gas water heater How to install gas water heater
	Test piezo igniter The piezo igniter might not be giving spark to relight pilot? Buy: Piezo igniter Resource: Test piezo igniter Hot surface igniter troubleshoot How to light gas water heater
	Thermocouple or thermopile? Electronic gas control (top row on image) has thermopile if unit is not pilotless Thermopile is several thermocouples together, so voltage produced by heat of pilot is large enough to power electronics inside gas control. Resources Test thermocouple Test thermocouple and thermopile/ pdf Mechanical gas control (lower row on image) has thermocouple Troubleshoot by type of gas control
Thermocouple is 2 different metals with tip sitting in pilot flame. When heat is applied, small current is created that travels to gas control valve through copper tube. If no electric signal is received as gas control valve, then small magnet closes off gas supply. Thermopile is a cluster of thermocouples. More current is created, and current travels to gas control valve through small wire. The larger current is enough to power computer chip and error-code indicator light at the gas control valve. If no current is received, the chip closes off gas supply to gas control valve.
Steps start here
Door and burner assembly are removed to replace thermocouple Larger image	Whole assembly is replaced Newer models 2009- current (depending on brand and model) Typical 6-year tank has 6 years parts and tank, so the part is covered 6 years, labor covered year 1. Contact manufacturer with model number, serial number, to find exact part number and warranty coverage. Water heater manufacturers Age of water heater Generic steps for replacing burner parts
Some brands require separate door gasket. Should have gasket on-hand in case removing door causes gasket to tear.	Some models Gasket may be needed Generally, water heaters from Rheem, Ruud, Richmond, GE, etc might require separate door gasket. Remove carefully if gasket is reused. Water heaters from AO-Smith, American, State, Reliance, Kenmore, Whirlpool might have one-piece door and gasket that is reusable Read product manual to identify parts. If you do not have manual, look at label on side of water heater to identify company Water heater manufacturers
	General location of Thermocouple Note: end of Thermocouple must sit in the pilot flame. Heat from pilot creates small current that travels to gas control valve, and keeps control valve open so gas will flow to pilot and burner. If thermocouple falls away from pilot flame, or flame goes out, the absence of electric current will turn off gas to pilot and burner. This type thermocouple requires removal of burner from combustion chamber

	Step 1: Turn off gas Locate gas shut off. Handle parallel with gas line => Gas ON Handle perpendicular across gas line => Gas OFF Rotate gas shut off handle perpendicular across line to shut gas OFF.
	Step 2: Notes before starting Note each tube connected on bottom of gas control. Note how tight each is when removing, so re-installation is about same. a) Thermocouple connection is finger tight plus 1/4 turn b) Manifold tube carries gas to burner c) Pilot tube carries gas to pilot light Gas has less psi than water, and connections do not need to be as tight. Do not overtighten. These connections do not need pipe sealant or teflon tape. For propane, manifold tube threads are reverse. Natural gas, threads are regular.

Step 3: Remove screws
Remove screws holding door

AO-Smith, American, State, Reliance, Kenmore, Whirlpool have hex screw
Rheem, Ruud, Richmond, GE have tamper-proof screws.
Use punch to break out center, and hex to remove

Look upward, and to one side, through sight glass to see that pilot flame is lit and clear blue color.
Causes for pilot outage:
Backdraft from shared vent and wind coming down the flue can blow out the pilot. see section 11 for venting. Dirty combustion parts and need for maintenance can also cause outage. see section 7. Bad thermopile or thermocouple. Misaligned thermocouple can also cause outage. Modern water heaters have solved the misalignment problem with fixed positioning and 1-piece replacement for combustion parts. see section 7. Bad gas control valve can cause pilot outage. see section 6.

Pilot light troubleshoot:
Clean the air intake, and get more fresh air to unit.
Push in TCO located on front of combustion chamber.
Pilot troubleshoot resources
Test thermocouple
How to light gas water heater
Pilot light goes out
Burner goes out when control knob turned to ON
Pilot light will not stay lit/ pdf
Pilot outage/ pdf
Pilot problem or ECO or gas control?
Wind blows out pilot light
Pilot light or thermocouple?
Negative pressure blows out pilot

Pilot tube orifice
Clean with compressed air or carburetor cleaner
Do not rub with rag, or tube can clog

Buy
Tip cleaner

Pilot troubleshoot resources con't
Standing pilot light maintenance
Attic Ventilation and Pilot Outage
Pilot outage and negative pressure
Pilot light maintenance/ pdf
Ventilating tight-house/ pdf
Pilot light troubleshoot

Manifold tab fits into bracket	Step 4: Remove burner Be careful Do not dump debris off the burner where it can fall down onto arrestor screen Burner will hook into a slot, or slide out from under a holder, or slide out of a slot. Refer to product manual for illustration. AO Smith-American-State-Reliance-Kenmore-Whirlpool manuals generally have clear instructions and illustrations. Do not expect Rheem-Ruud-Richmond-GE manual to have illustrations or instructions.
Manifold tab fits into slot, or bracket DO not dump debris off burner
Prevent clogging	Step 5: Carefully vacuum out combustion chamber Keep stuff from falling down onto the air intake screen
	Step 6: Get ready to replace Take photos Mark-n-measure where new thermocouple should fit End of Thermocouple must sit in pilot flame 3/8"-1/2" to work correctly Pilot assembly will be held in location with screws Step 7: Replace Remove thermocouple by slowly, firmly pulling and twisting from bracket If thermocouple will not disengage from pilot assembly, then replace entire assembly Removal from door might be easier by cutting copper tube with wire cutter Tip of thermocouple or thermopile is 3/8" to 1/2" into pilot flame There will be a grommet-type holder to keep thermocouple in place. Replace thermocouple pdf
Image shows 3-legged water heater This type water heater is easiest to clean without removing combustion parts.	Step 7: Clean the air intake before putting parts back Rheem, Ruud, Richmond, GE air intake screen located below combustion parts. AO Smith, American, State, Reliance, Craftmaster, Kenmore, Whirlpool the air intake screen located bottom of heater. Use compressed air. Use borescope, or mirror and flashlight to inspect. Clogged air intake screen will cause overheating. Move boxes, rags, etc away from water heater for improved air flow Slow incoming air supply, causes slower venting, yet same amount of gas is burned. Slow venting with same amount of BTU output will overheat combustion chamber, and trip FV system. Each manufacturer has different steps for repairing FV overheat, depending on Brand, Age, Model, etc of water heater. DO NOT USE HARD BRISTLED BRUSH ON ARRESTOR SCREEN Use soft brush, paint brush, compressed air, vacuum cleaner.
	LP and NG models vary Rule of thumb is .125" [or thickness of nickel] Igniter and pilot must be positioned closely so gas escaping the pilot orifice will flow into hot ignitor. Once the pilot ignites, the tip of thermocouple or thermopile must be in the pilot flame.
Larger image	Step 8: Re-install burner Reinstall burner. Wait to reattach door screws until tubes are connected. Re-connect tubes to gas control valve before attaching combustion door screws. Manifold tube on LP gas water heater is reverse thread. Do not overtighten tubes. Remember how tight each connection was when removing. Thermocouple is finger tight + 1/4 turn. If thermocouple is overtightened, the electric current produced by thermocouple will short out against gas control valve, and gas control will shut off gas to burner and pilot. Can result in damage to parts and water heater will not function and pilot will not stay lit. Reinstall combustion door screws, with gasket properly aligned, and sealed
	Step 9: Turn on gas Turn on gas to water heater Check all connections for gas leak using soapy water. Use chloride-free soap and water Propane is heavier than air, so smell close to floor Natural gas is lighter than air, so smell higher Give leak time to show itself, since gas pressure is lower than water pressure Step 10: Light heater Light gas water heater using instructions printed on side of water heater. Gas flame should be clear blue, with small amount of yellow and some red.
	Step 10: More Options A) Call service technician to fix water heater B) Continue troubleshooting: How to troubleshoot gas water heater How to repair Rheem FVIR C) Install new water heater How to install gas water heater Recycle old water heater
	Troubleshoot pilot flame Tip of thermocouple or thermopile is 3/8" to 1/2" into pilot flame It may be hard to see pilot flame on some models Sight glass location varies by model of water heater People often do not get low enough to see pilot flame. When viewing pilot flame, generally you must look upwards through sight glass and to the right.

Resources:
Replace thermocouple with Unitrol gas valve .pdf
Replace thermocouple .pdf

Test thermocouple I .pdf
Test thermocouple/ thermopile .pdf

Generic replacement steps for replacing burner .pdf
Cleaning the burner .pdf
Burner cleaning

What you need for operation of gas water heater.
1) Basic parts and operation
2) Adequate incoming air supply ... issues: closed doors, tightly insulated house, very hot attic.
3) Adequate air supply getting to burner... issues: dirty vent screen, dirty environment, maintenance.
4) Thermal cutoff ... TCO ... issues: failed part, maintenance, vent.

5) Flammable vapor lockout .... issues: exposure to vapors, bad FV sensor, failed FV system,
6) Fuel supply to gas valve thermostat ... natural gas and propane are different ... issues: wrong gas, low pressure, moisture in pipe, undersized gas meter, supply line too small for BTU rating.
7) Gas valve thermostat regulates fuel supply ... issues: not enough gas, failed thermostat, failed gas control valve.

8) Fuel supply from thermostat to burner ... issues: maintenance, thermocouple-thermopile, gas control valve.
9) Clean and replace burner ... issue: periodic maintenance requires burner inspection, cleaning, and possible replacement

10) Functioning thermopile-thermocouple-pilot light ... issues: misalignment, failure of part.
11) Ignition of fuel supply by pilot light or hot surface igniter ... issues: pilot light, piezo igniter, electrode.

12) Power vent water heater troubleshoot ... issues: pressure switch, blower, blower sequence from gas control, outlet polarity
13) Venting combustion byproduct .... issues: vent in disrepair, other vents in house drawing air

14) Misc troubleshoot manuals

Troubleshoot Gas valves with manuals

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